Motor positioning device



June 4, 1963 P. E. SMITH, JR., ETAL I I l l I I Q |Z35| l I I l I I Q:I248: 246 2% %-za9 I 2 6 Sheets-Sheet 1 Ill- IN VEN TORS EZEKIEL WOLF.WOLF 8: GREENFIELD June 4, 1963 Original Filed April 9, 1956 P. E.SMITH, JR., ETAL 3,092,742

MOTOR POSITIONING DEVICE 6 Sheets-Sheet 3\fIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIQ I III] 2% z. m'wgm BY141w, a. 91.11

EZEKIEL WOLF, WOLF 8: GREENFIELD J1me 1963 P. E. SMITH, JR., ETAL 3,09

MOTOR POSITIONING DEVICE Original Filed April 9, 1956 6 Sheets-Sheet 4 5wukha WGRSK .ZDUMIU n24 um I 3a muZOTCmOa INVENTORS g d, 1- M9 law! 42..9 EZEKIEL WOLF, WOLF a GREENFIELD Hm/L, W

1 0 ZQESBQ Mu! aOm JQZQR mmw June 4, 1963 P. E. SMITH, JR., ETAL3,092,742

MOTOR POSITIONING DEVICE 1 Original Filed April 9, 1956 6 Sheets-Sheet 5n 1963 P. E. SMITH, .IR., ETAL 3,

MOTOR POSITIONING DEVICE 6 Sheets-Sheet 6 Original Filed April 9, 1956TORS INVEN muHL BY 1km, LL. $1

xmjomhzou 52am m 6 0 EZEKIEL WOLF WOLF & GREENFIELD ire ts This is adivisional application of application Serial No. 576,928, now Patent No.2,948,839, and relates to a positioning device and control means forsupplying an input electrical signal to the positioning device, with theinput electrical signal being derived in the control means from aselected external variable.

The present invention is a further improvement and extension ofcopending patent application Serial No. 534,020, filed September 13,1955, now Patent No. 2,948,295, dated August 9, 1960.

In the present invention there is provided an electrically operatedpositioning device adapted to position a variety of elements such asvalves, guide bars, rods, cutting edges, Potentiometers, resolvers, orother elements, used in computing devices to be used in analogcomputation or in analog digital data conversion, or in the variousmoving parts of automatic machine tools, such as milling machine heads,table and/ or tool holders. In addition to these uses, the positioningdevice and its control system may be used for any application wheretranslational motion control of a particular object is desired.

In the present invention, however, the mechanical and electricalarrangements are described in connection with their use as a valvecontrol for which the invention is particularly adapted. If, however,other applications of the invention are to be made, the valve stem mayreadily be replaced by a suitable linkage or gearing system so as tocontrol the operation of some other desired implement, such as a roll,carriage, potentiometer, or other element being positioned.

In the present invention, the positioning device is provided withmechanical means electrically operative of unique and efficient design,so arranged as to provide a greatly improved positioning device whichpermits a more accurate and responsive positioning to a given signalthan heretofore has been obtained. Broadly speaking, the presentinvention provides an electrical controller unit and a positioner unithaving a mechanical structure operatively controlled by an electricalcircuit (defined hereinafter as the electrical positioner circuit so asto distinguish it from the electrical controller circuit).

In the positioner unit there is provided an improved means of limitingthe reciprocal limits and motions of the actuating element or stemconnected to the valve or other controlled element as well as improvedmeans for providing a braking to the input power so as to avoidover-running.

The present invention also provides a fail-safe system in which themechanical structure will always remain in either a chosen open orclosed position in the event that there is a power failure and currentto the system is thereby cut off.

There is also provided in the present invention, a control device ormeans of improved design. This con trol device is designed to receive aconstant or variable input signal and compare it with a desired constantor variable input level, so as to obtain a selected output signal whichis used as an input to a second stage, with the second stage orelectrical positioner circuit directly controlling the operation of themechanical structure.

The control device itself provides a stable and eflicient tet system forsupplying a constant or intermittent controlling signal to thepositioner unit and is particularly adapted to receive Widely varyingvariable input signals representative of actual parameter values whichsignals are compared with a variable or fixed reference desired signalrepresentative of a value for that parameter.

In the operation of this control device, preferably three signals are infact, utilized for the purpose of obtaining the desired signal. Thesesignals are an integral, proportional, and derivative signal, with eachderived from the error signal representative of the deviation of theactual signal from the desired signal. These three signals, integral,proportional, derivative, are summed within the control device, and thesummation is used as the input to the electrical positioner circuitcontrolling the mechanical structure. In addition to the features of thecontrol device set forth above, there is also provided means in thecontrol device for selecting a zero center, and for manual operation ofthe controller in such a way that the controller may be switched frommanual to automatic without any noticeable effect in the electricalsystem taking place. Other features and advantages of the presentinvention will be considered in connection with the accompanyingdrawing, in which:

FIG. 1 is a cross sectional side elevation of the positioner mechanism.

FIG. 2 is a front elevation in partial cross section.

FIG. 3 is a cross section taken along the line 3-3 of FIG. 2.

FIG. 4 is an openly folded partially cross sectional view of the motorand gearing assembly.

FIG. 5 is a modification of a portion of the positioner mechanism.

FIG. 6 is a further modification of a portion of the positionermechanism.

FIG. 7 is a schematic electrical circuit of the electrical means foroperating the positioner.

FIG. 8 is a schematic electrical circuit of a modification of the schemeshown in FIG. 7.

FIG. 8a is a schematic electrical circuit of another modification of aportion of the invention described in FIG. 7.

FIG. 9 is an electrical circuit showing the schematic arrangement of thecontroller used to supply a signal to the circuit shown in FIG. 7.

FIG. 10 is an electrical block diagram showing a further modification ofthe invention, and

FIG. 11 is a block diagram of the various electrical components of thepresent invention. I

Referring specifically to FIG. 11, there is shown in block arrangement,overall means of operation of the present invention. This generalarrangement has been previously indicated in the above-mentionedcopending application, and accordingly only a brief rsum will be made atthis time. In this arrangement a particular variable, whose value is tobe controlled, as previously indicated, is measured by a suitablemeasuring device 2, such as flow meter, pyrometer or the like. Thesignal thus obtained is converted to an electrical signal and isamplified through any suitable electrical network 3. These elements 2and 3 do not form a portion of the present invention, except insofar asthey are utilized to provide a proper signal to the controller andpositioner amplifier. The signal, as derived from the electrical network3, is then fed to the command signal source 4 where it is compared withrespect to a desired value signal obtained from a suitable signal source5. The differentiated and integrated output signal from this controlleris then used as an input signal to the electrical circuit 6. The outputof the source 4 is then representative of the desired valve posi tion.The electrical circuit 6 compares the signal from the command signalsource 4 with the signal from the valve position transducer 2a,characteristic of the actual valve position, and actuates the motor unit8 to position the valve 9 until its position coincides substantiallywith that representedby the output signal from the command signal source4.

In describing the structure and operation of the present invention,consideration will first be given to the mechanical structure of thepositioner or positioning device itself, then to the electrical circuitcontrolling its operation, and finally to the controller unit and themodification of the invention.

For convenience, reference will be made to the use of the invention forcontrol of a valve stem which in turn operates a valve regulating theflow of a liquid, depending upon a temperature resulting from the actionof the flow of said liquid upon the process. It should, however, beclearly understood that this invention may be materially extended inusage as previously indicated.

Referring now to FIGS. 1, 2, 3 and 4, there is illustrated therein themechanical structure of the positioner device. In this structure thereis provided a casing 2%, having an upper casing section 261, for themotor mechanism secured by bolts 202 to the lower casing section 203.This lower casing section encloses actuating mechanisms which areadapted to be secured to the valve stem controlling the fluid flow, andis provided with openings on either face to facilitate access to themechanism. In this structure a motor 225 is mounted by suitable meanssuch as posts 296, on the transversely extending plate or support 204.

As illustrated a single motor 205, capable of operating in bothdirections is utilized, although a pair of single directional motorsarranged to cause rotation in opposite directions may also be used withsuitable interconnecting gearing. As illustrated, this motor 205 has ashaft 210 with a gear 269 mounted thereon which meshes with the gear211. The gear 211 is in turn mounted on shaft 212 and carries the piniongear 213. This pinion gear 213, is adapted to be engaged by the gear214, mounted on the shaft 216. This shaft 216 is journalled in andlongitudinally slidable in the fixed collar 217, but is normallymaintained in a position so that the gears 213 and 214 may be engaged bythe action of the leaf spring 218 which contacts and presses upwardlyagainst the lower end of the shaft 216. The spring 218 is secured to thelower side of the support 297 by a nut and bolt arrangement 219. Alsomounted on the shaft 216 is a pinion gear 226 which engages the gear221mounted on the shaft 222.

A hand wheel 223 on the shaft 224 telescopically en gages the shaft 225.The shaft 224 has mounted on it the gear 226 provided withoutwardlyextending flange 227 at its upper end which is adapted toengage the upper surface of the gear 214 when the shaft 224 is moveddownwardly. This shaft 224, however, is normally maintained in an upposition by the helical spring member 229. If desired, a spring latcharrangement 230 may be provided on the top of the casing to engage arecess or groove in the shaft 224 to insure that it is normallymaintained in its upright position.

By releasing the latch 230 and pushing down on the shaft 224 the gear214 may be disengaged from the gear 213, thus permitting a handoperation of the device hereinafter described, while at the same timeinsuring a complete disengagement of the motor so as to avoid anyaccidental operation of the device by the motor when hand operation isdesired.

The shaft 222 is mounted in a bearing collar 232, which in turn iscoaxially mounted in the plate 2&7. At the lower end of this shaft 222,is coaxially fixed a threaded shaft 235. This threaded shaft 235 hasmounted upon it a non-rotatable nut 236. This threaded shaft and not arepreferably provided with ball bearing interengagements for increasedefiiciency. This type of screw and nut arrangement is manufactured bythe General Motors Corporation, under the mark Saginaw Ball Nut & LeadScrew.

The nut 236 is rigidly secured to the cross member 237.

This cross member 237 has secured to it a pair of oppositely arrangeddownwardly extending parallel rods 238, which are mounted forlongitudinal movement in sleeve bearings 239. At the lower end of theserods, is provided a second cross member 2 40', suitably secured, such asby nuts 250. Cross member 240 is provided with a centrally locatedsleeve 241, in which may be secured any suitable actuating typemechanism which is adapted to extend downwardly through the opening 242to operate the valves which are being controlled. If desired, atransverse hole in the sleeve 241 may be provided for locking themechanism placed in the sleeve in position.

The lower end of the threaded shaft 235 is fixed in a ball bearingmounting 243 in turn mounted within the lower portion 244 of a sleevemember. The ball bearing race 243 may be secured in position by a nut245. The lower section 244 of the sleeve member, is rotationally fixedbut is adapted to move vertically responding to vertical movements ofthe threaded shaft 235. The other portions of this sleeve member includethe annular lower sleeve section 246 and the upper sleeve section 247,which are interconnected by the annular ring 248, suitably securedrespectively at its inner edge to the section 247 and its outer edge tothe section 246. This sleeve structure is tensioned downwardly by theloaded helical spring 251, positioned between the sleeve section 247 andthe inner surface of the lower wall 203, of the casing. The lower end ofthis spring 251 bears against the ring 248, while the upper end of thespring bears against the wall 252 which forms the bottom surface of theupper casing section 20 1. Downward motion of the sleeve structure maybe limited by the flange or ring 253 which is secured about the top ofthe sleeve section 247. An extension 254 is rigidly secured at one endto the top of the upper sleeve section 247 and extends outwardly in aposition to contact the microswitch 255 and thereby actuate it upon anupward movement of this arm 254. This microswitch, as will be moreclearly understood from the description further on, is connectedelectrically in series with the power supply to the motor when actuated.

On the sleeve 241 there is provided an adjustable arm 256 which isadapted to actuate the microswitch 257, when the sleeve is moved upwardsto a limited up position. Also provided on the sleeve 241 is a rack 258,FIG. 3, spring tensioned firmly against the gear 259 by means of theleaf spring 260. The rack 258 and leaf spring 260' may be secured to thesleeve 241 by suitable means. The gear 259 is mounted on the shaft 261which controls the potentiometer 262 at its other end. This shaft 261may be journalled in supporting brackets on plates 263 and 264. Ifdesired, the brackets 264 may be extended downwardly and calibrated atits edge so that the pointer 265 secured to the sleeve 241 may be usedin connection with the calibrations on the plate 264 to determine anexact relative position of this sleeve and thereby the position of thevalve stem or valve operated by the sleeve.

The potentiometer 262 is utilized as a position measuring or sensingdevice in the feedback portion of the electrical circuit which operatesthe motor or motors actuating the valve stem. Other position sensingdevices, however, may be used, provided they are adapted to be convertedto an electrical feedback signal for use in the electrical circuit ashereinafter appears. Alternate arrangements for mounting the feedbackpotentiometer are possible. One such arrangement consists of a five turnpotentiometer mounted within housing 201 suitably provided with a gearfixed so as to mesh with gear 221.

The spring and rack arrangement is designed to eliminate backlashbetween the rack and gear without permitting wear or binding on thevarious elements.

' A braking mechanism is provided to the armature of the motor 205 bymeans of a brake plate and brake shoe 270 and 271 respectively, with thebrake plate 270 secured to the armature shaft and the brake shoe 271secured to the core of the solenoid 273. This solenoid 273 is mounted bysuitable means. such as the bracket, stand pins and plate assembly 274,directly above the motor 205. The core of this solenoid 273 ismaintained in a normal up position by the helical spring member 275secured at one end to the core of the solenoid and at the other end tothe bracket plates 277. When the core is in its normal up position, thebrake shoe and the plate are disengaged, permitting free rotation of thearmature and conversely where the core is in a down energized position,the brake is on.

In the operation of the mechanical portion of this invention, the motor205 will rotate in response to an input signal in either directiondependent upon the sign of the signal, causing a consequent rotation ofthe threaded shaft, 235 through the gearing previously described.

When this threaded shaft rotates, the nut 236 which is rotationallyfixed to the rods 238, will move up or down in response to theparticular direction of rotation of the shaft 235. This will, of course,control the up and down movement of the sleeve 241, and the valve stemattached to it. The switch 257 is provided in series with the powersource to the motor to limit the upward movement of the-sleeve 241, forwhen the arm 256' contacts the switch, the power to the motor willconsequently be turned ofi, stopping the positioner in that particularposition.

In the event that the valve, valve stem or sleeve meets with some sortof obstruction on its downward movement, the continued rotation of thethreaded shaft 235 causes this shaft to move upwardly in the lowimmobile nut 236. This upward movement of the shaft 235 carries upwardlywith it through the bearings 243, the sleeve structure, includingsections 245, 247 and 249. As the spring 251 bears against the ring 248of this sleeve structure, there begins at a selected pressure, acompression of the spring 251. The force necessary to compress thisspring has been previously determined at a selected value. Whenadditional force tending to raise this sleeve structure is applied, thesleeve structure itself will begin to move upwardly against thecompressing spring 251 until the extension or arm 254, FIG. 2, on theupper end of this sleeve structure engages the microswitc-h 255 causingthe power to the motor to be cut off. Because the solenoid 273 is soconnected to the power source as to be energized when the motor is cutoff, the brake shoe and plate 271 and 270 will engage, preventing themotor armature from freely rotating, and thus, by braking, maintain theoriginal force on the valve, valve stem and sleeve 241, which was beingapplied at the time the microswitch was actuated. Because of this thevalve will remain in the exact position at which it was located when themicroswitch was actuated.

In the illustration of FIG. 5, there is illustrated a modification ofthe present invention, in which a fail-safe operation is provided toautomatically move the valve to a downward or closed position in theevent of a power failure. In this structure the nuts 236a, threadedshaft 235a, sleeve section 246, 247 and 249' are similar to thosepreviously described. In this structure, however, a plate member 280secured by suitable means, such as screws member 252. A helical spring283 coaxial with the shaft 235a has one end bearing against the plate280 and the other end bearing against the flange 284 formed on top orsecured to the nut 236a. This spring tensions the nut 236a downwardlytowards a closed position so that upon power failure the nut 236a andthe mechanism carried by it, including the valve, will move downwardlyto a closed position. In order to prevent this spring from operatingduring the normal operation of the positioner, causing the member 236ato move from its desired position, the electrically operated solenoidbrake, illustrated in FIG. 4, is wired so that the solenoid 273 isenergized to hold the brake shoe 271 against the brake plate 270whenever the motors are not running. If the electrical power fails,however, the brake will be off, being kept off by the spring 275 whichpermits the spring 283 to force the nut 23min downwardly.

In the illustration of FIG. 6, there is shown fail-safe modification inwhich the valve stem is maintained in an open position on failure of theelectrical power source. In this structure a downwardly extending sleevemember 296 having an inwardly turned lower flange 291 and upperperipheral flange 283 is secured by screws and nuts 284 in spacedrelation from the plate 252. Also fixed to the nut 236a is thehorizontal engaging flange 292 and the upwardly extending sleeve member292a. An expansion helical spring 293 is positioned about the screw235!) with its ends between the inwardly extending flange 291 and theflange 292, providing an upward tension to the nut 235a. Upon failure ofthe power in the system, this spring actuates to raise the nut 236a andconsequently moves the actuating arm upwardly. In order to insure thatthis spring does not interfere with proper operation of the motor, ascheme similar to that described in connection with FIG. 5 is utilized.In this arrangement, however, the solenoid 273 is actuated to engage thebrake shoe and brake plate only when the motor is deenergiz-ed. When,however, the motor is energized or when the electric power fails, thesolenoid 273 is deenergized, permitting the spring 275 to disengage thebrake and thereby permit the spring 293 to raise the valve. Thisoperation may be obtained as in the modification of FIG. 5 by connectingthe solenoid 273 in series with the terminal of the relay switcheshereinafter described in connection with FIG. 7.

Reference is now made to the electrical positioner circuit illustratedin FIGS. 7 and 8. As previously indicated, the motor 205 for operatingthe mechanical structure may be replaced by a pair of motors, as isillustrated schematically in FIG. 7 where the motors are represented bythe field windings and 102. These motors 100 and 102 are mounted intandem with preferably a common armature axis or some equivalentstructure or gear train by which the screw 235 may be reversely rotated.These motors 100 and 162 are counter-revolving so as to provide thisreversible rotation.

These counter revolving motors 100 and 102 are operated by a desiredvalue input signal fed through the line 104 which is derived from thecontroller device hereinafter described or from any other controllercapable of furnishing the signal on line 104. This desired value inputsignal 164 is compared with a signal derived from the actual position ofthe valve by such means as the potentiometer 262, previously described,which is magnitudinally adjusted by movement of the sleeve 241. Thepower through the potentiometer 262 in series With the lines 1% may beobtained from a suitable power source 167. An alternate arrangement ofpower source and potentiometer 262 may be used wherein potentiometer 262is connected as a voltage divider. The resultant signal which isproportional, therefore, to the difference between the actual valveposition and the desired valve position as indicated respectively by theoutput valve position signal and the desired valve input signal isamplified in the magnitude amplifier or transistor amplifier 108 toobtain either a positive or negative signal which is reflectedrespectively in either the relay 110' or 112 or into appropriate coil orcoils of a polarized relay. If a resultant signal, for example, isobtained in relay 110, the relay switch 114 closes the relay contact 116completing a circuit through the line 118, the motor 160, line 121) andpower source 122. If, on the other hand, a signal of opposite sign isobtained in relay 112, a circuit is completed through the motor 102 byclosing of the relay switch 124 to the contact 126, with the circuitbeing completed through the power source 122, field coils 102 and line128. As these motors have a tendency to overrun their desired stopposition, means are provided in this circuit for providing aunidirectional pulse of current through the motor windings, whereby adamping sufiicient to suddenly stop the motor is obtained, and therebyprevent the motor from overrunning its desired stop position. This meanscomprises the relay 130 which is connected in parallel with the motorsby the line 132. When either motor 100 or 102 is running, the relay 130will also be energized. When relay 130 is energized, the relay switches134 and 136 are closed to contacts 138 and 140 respectively. When thusconnected, the con denser 142 in the line 144 between the relayswitches, is connected across the direct current source such as therectifier, as illustrated at 148. This rectifier charges the condenser142 through the lines 150, during the time interval that the motors 100or 102 are running. When the motors have operated so that the positionof the valve stem controlled by the motor is suificiently close to thedesired position, current actuating the motor is reduced to zero by theopening of the relay switches 114 or 124. These relay switches 114 or124 then normally close respectively to the contacts 152 or 154.Simultaneous with the deenergizing of the switches of relays 110 or 112,the relay 130 will also be deenergized permitting the switches 134 and136 to close their normally closed positions in contact with thecontacts 156 and 158respectively. This will thereby permit the charge onthe condenser 142 to discharge through the contacts 156 and 158 andlines 160 and 162, switches 11 4, 124, lines 118, 128 and the two motors100 and 102, thereby producing the desired unidirectional pulse ofcurrent, which pulse provides a suflicient eddy-current damping to bringthe motor to a sudden stop and thus prevent an overrunning. In thisconnection it should be noted that the charge on the condenser 142 issubstantially proportionate to the length of time the motors 100 and1102 run, and therefore a greater charge on the condenser is availablewith an increased velocity of the motor.

The solenoid 273 which operates the brake on the motor 205, aspreviously described, is connected across the relay switches 170 and 171which in :turn will close to the relay contacts 172 and 173 respectivelywhen relay 130 is deenerg-ized. These contacts in turn are connectedacross the lines 150. Then the solenoid 273 will be energized when themotors 100 and 102 are not running. Conversely, when either motor isrunning and relay 130 is energized, solenoid 273 is deenergized. Thissolenoid will also be deenergized when power fails.

In FIG. 7 there are also illustrated the microswitches 255 and 257adapted to cut 011 power to the motors in the event of overdriving theshaft 235 in either direction.

The circuit illustrated in FIG. 8 is operative in the same manner asthat described in FIG. 7 with the exception that the condenser 142a isconnected across the single motor through the line 132a for the purposeof providing a proper phase shift. The relay 130 is also connectedacross the motor 101. In this modification, the motor is driven ineither direction dependent upon the source of the signal received. Afurther modification, which utilizes master and slave relays thuspermitting the use of motors of a higher power rating, is shown in FIG.8a. This modification shown in FIG. 8a and hereafter described ispreferable.

The controller section most clearly shown in FIG. 9 provides a suitablemeans for deriving a signal input to the electrical portion of thepositioner. This controller may derive its signal from any variablecapable of being electrically measured, such as pressure, temperature,flow or thickness. These measurable quantities are, of course, utilizedas a measure of the operation of some process which may be influenced bythe movement of the actuated mechanism in the positioner, as forexample, the flow of a liquid which might be controlled by a valvemounted on the positioner. The signal measured by the controller iscompared with a fixed or variable desired value and the deviation orerror between the actual value and the desired value is determined. Thisdeviation, suitably processed, then becomes the input to the electricalpositioner circuit. The desired value may be prefixed by actual humanmeasurement or may, on the other hand, be determined by measurements orcalculations obtained by some other type of controller unit. Thecontroller unit utilized in the present invention, in addition toamplifying the deviation or error prior to feeding it into theelectrical positioner circuit, also provides a means for producing thesum of three signals, one proportional to deviation, one proportional tothe integral of deviation, and one proportional to the derivative of thedeviation. Further, the controller may also be used for varying theproportionality factor between the deviation, its input, and its outputsignal to the electrical positioner circuit. This output is utilized asthe input or desired value measure for the positioner mechanismpreviously described.

In the present circuit where the output signal provides a sum of threesignals including proportional to deviation, proportional to integral ofdeviation and proportional to the derivative of the deviation, the inputsignal from the prime measuring means is received at terminals 300 and301. This signal is transmitted through the switch 302 and lines 303 and304 to the amplifier stage, where depending upon the signal received inthe lines 305 and 306, an output signal will be obtained in either ofrelays 308 or 309. The lines 305 and 306 provide a feedback signal,which increases until it reaches a voltage equal to the input voltagereceived, through the terminals 301 and 300 thereby deenergizing therelays 308 or 309 at a desired instant. This feedback system will bemore clearly described hereafter.

The resultant signal obtained by the difference between the actualsignal and feedback signal may be either positive or negative and willaccordingly operate either relay 308 or 309. The signal received in therelay 308 for example, will thereby close the relay switch 310 to thecontact 311.

When relay switch 310 is closed to the contact 311 the motor 312 isactuated and starts to run. The power to this motor is supplied from thepower source 314, through the line 315, switch 310, line 316, the motor312, to the other side of the power source. Simultane ously with therotation of this motor, the capacitor 317 begins to charge until itreaches a voltage approximately equal to the voltage of the input signalon the lines 303, 304. This charge in the capacitor 317 is derivedthrough the lines 318 and 319. As the power source 314 may be A.C.voltage, a rectifier 320 is provided in the line 318. The charge builtup across this capacitor 317 is discharged through the line 321, filternetwork 322 and line 323 to the potentiometer 324 and line 305 on oneside, and, on the other side through line 319, potentiometer 325, line326, line 327, to switch 328 and line 306. When the voltage thus derivedin lines 305 and 306 equals the voltage in lines 303 and 304, relay 308will be deenergized, thus permitting the relay switch 310 to close toits normally deenergized position to relay contact 330. When thisoccurs, the capacitor 317 will discharge through the resistor 331,lowering the effective voltage across this capacitor 317, and therebyreducing the feedback input signal on the lines 305 and 306. When thisinput signal on the line 305, 306 is reduced, the relay 308 will againbe actuated, repeating the cycle previously described. Each time thisrelay switch 310 is closed to contact 311, the motor 312 will run. In asimilar manner, if the signal derived from the difference between thesignals on the lines 303, 304 and 305, 306, is opposite from thatpreviously described, relay 309 will be actuated causing the motor 335to be actuated in an opposite direction causing condenser 336corresponding to condenser 317 to charge, and thereby provide a feedbacksignal through the lines 305, 306. Thus in the operation of the motors312 and 335, they will run intermittently with the length of runningtime to oft time, proportional to the input signal 370. The capacitorcircuit described,

small, to a maximum when this input is large.

insures that these motors will maintain their average velocity inproportion to the input signal on lines 303, 304. The average velocityof either motor is thereby varied from a minimum when the input in thelines 353, 3854 is ince the rates of angular rotation of the motors 3-12and 335 are proportional to the input, the angular distance of rotationof the motor shafts is proportional to the integral of the velocity, or,consequently to the integral of the input of the lines 303, 304. Thisintegral measure is converted to a voltage measure through control ofthe potentiometer 340, mounted directly or by suitable gears, asindicated by the dotted line 341, to the motors. As previouslymentioned, the voltages across the capacitors 317 or 336, areproportional to the input on lines 303, 304-, with the voltage beingimpressed across condenser 317 dependent upon the input of one signalacross condenser 336 upon the input of the opposite sign. Consequently,the voltage across points 349 and 350, is proportional to the input andis therefore used as a proportional signal. This signal is impressed onthe output through the lines 327 and 323, and the lines 351 and 352. Inaddition to .this proportional signal, there is impressed a simultaneousderivative signal which is obtained by measurement of the averagecurrent into either the capacitor 317 or 336. This is obtainable as thecapacitors 317 and 336 have a voltage across them which is proportionalto the input. Because of this, the average current into either of thesecapacitors is proportional to the derivative of the voltage across themand consequently, the average current into the capacitors isproportional to the input. Therefore, by providing a resistor 353, whichmay be in the form of a potentiometer, in the line 313, and tapping itthrough the line 326, a measure of the current into either of thecapacitors 317 or 336 may be obtained. Since the voltage across thisresistor 353 is proportional to the current into the capacitors, it isconsequently proportional to the derivative .of the input signal inlines 303, 304. This derivative signal is thereby fed back to the outputalong with the proportional signal. This derivative feedback signal, itmay be noted, has an additional stabilizing eifect in the circuit.

Thus, the integral signal obtained across the resistance 360 is added tothe proportional and derivative signal obtained across the resistor 361,which as stated is tapped from the line 351. The derivative signal maybe varied and adjusted by the potentiometer 325 and the proportionalsignal used in the feedback may be adjusted by the potentiometer 324.Potentiometer 363 is used to adjust the integral signal. These signalsare thereby summed and impressed across the output 365. This output 365is used as the desired input to the electrical positioner circuit, FIG.7.

Provision is made in this circuit for a manual adjustment operativethrough the gang switch 369, which when actuated, will disconnect theinput signal across the lines 300 and 301, and connect the input signallines 353, 304 of the amplifier to the manually operated inputpotentiometer 370. This input potentiometer having an adjustable powersupply 371, thereby provides an adjustable input signal which willoperate the motors 312 and 335 as servo motors. Simultaneously, with theswitching to a manual input, the feedback circuit is disconnected at theswitches 372 and 373, with these switches engaging contacts 374 and 375respectively. This connection thereby provides a feedback to theamplifier which is proportional to the angular rotation of the motors312., 335. This signal is not proportional to the integral of the input,nor is there any derivative feedback. When the proper manual adjustmentis achieved and the input signal 303, 364 reduced to zero, the switch369 may be placed to its normal on position without altering the outputvoltage at the terminal 365 which had previously been kept equal to theinput of the amplifier by the servo action of the motors. In this mannera bumpless transfer is efifected.

The output 365 may be adjusted about a zero calibration by varying thepotentiometer 379 supplied by the suitable power source 376. This output365 may beused as a direct and continuous input to the electricalpositioner circuit of FIG. 7, or may first be fed through a samplercircuit which will limit the input signal to the electrical positionercircuit to a periodic sample. This sampler circuit is shown as a portionof the circuit of FIG. 9. in this operation, a timer motor 380 operatesthe cams 381 and 382, which periodically open and close in synchronism,the switches 333 and 384 respectively. When the switch 384- is closedcurrent will pass through the line 385 to impress the input signal onthe positioner circuit with the feedback being applied through the lines106. Simultaneously, the opening and closing of the switch 383 will openand close the AC. power source 122, which operates the motors and 102.By this circuit, the output of the controller unit, will be introducedperiodically as the input to the positioning device with a simultaneousobservation being made of the positioning device output 106 previouslydescribed, through the operation of the timer operative cams. If thevalue of the integral of deviation is different, from the valueindicative of the actual position, the electrical positioner circuit ofFIG. 7, will operate so as to provide correspondence. Theproportionality factor of the integrating mechanism is suitably adjustedby the potentiometers previously described, so that a properly stablesystem of operation is achieved in the sampling operation. Further therepetition rate of the sampling device may also be adjusted to insurestable operation by proper choice of a timing cycle. The mode of controlis such that if the integral of the deviation at the nth sampling timeis unchanged from the (rt-1th) time indicating zero average deviationbetween the (n1th) and the nth instant, no corrective action will betaken. It provides accurate control without unnecessary actuation of thepositioner in times between sampling. Such control can be stable in thepresence of large time delays or transportation lags in the process ordevice whose output is influenced by the position of the devicecontrolled in the positioner previously described.

As an additional means of control, the added circuit illustrated in FIG.10 may be utilized. With the realization that the deviations between theprocess variable actual value, for example, temperature, and the desiredvalue, are due to the efiect of disturbances, such as environmentalconditions, varying throughputs (production rates), varying raw materialproperties, varying demands and the like, an improvement in controlaction may be obtained by measuring said disturbing effects and adding asignal of properly chosen proportionalities to the signal previouslydescribed at the input to the electrical positioner circuit. The addedload or disturbance compensating signal is introduced in such a fashionas to cause the positioned member to move to such a position as tocompletely neutralize the disturbance. In order to aid in rapidlyneutralizing the signal, a signal proportional to the first or higherderivatives of the disturbance may be added as an input to thepositioner itself. Such a control is illustrated in FIG. 9 and includesin its structure an electrical network and amplifier 4%, connected to ameasuring device 401', which is utilized to measure the deviations inthe load or disturbance 402'. The signal in this electrical network andamplifier 4% is fed to the input of the positioner amplifier 453 inparallel with the output of the command signal source 404 as isschematically illustrated in this figure. This added load or disturbancethereby provides a compensating signal which will cause the positionedmember to move to a new position to completely neutralize thedisturbance.

In FIG. So there is shown an improved schematic circuit for operation ofthe present invention. In this circuit, the potentiometer 262 measuresthe actual output signal in a manner as previously described inconnection with the description of the valve positioner itself. Thevoltage derived through this potentiometer 262 is added to controlsignal derived from the controller through the lines 400 and 401. Thepotentiometer 262 forms a portion of the circuit illustrated in theenclosure 406. This circuit permits either a manual or an automaticactual output signal to be added to the controller. The controller andactual output level signal are fed across the lines 400 and 4111 to thelines 404 and 405 which are the input lines to the amplifier 403. Thesignal derived and fed into the amplifier 403, when it exceeds a certainvalue, will cause a current to flow in either one or the other of theslave relay coils 408 or 409. This in turn will cause the switch orcontact associated with that particular coil to close, actuating therelay coil 410 or 411 depending upon whether coil 408 or 409 was the oneactuated by the amplifier. When either of coil 410 or 411 are energized,all the contacts associated with that particular coil will be moved fromone position to another in the manner described hereinafter. Thus, ifcoil 410 were actuated, the switch 410a will close from no, to n causinga current to flow through the motor 1111 from the power source 122,completing the circuit through the switch 410a. This thereby energizesthe motor 101 which will rotate in a direction to reduce the errorsignal input into the amplifier 403. Simultaneously, the switch 41Gbwill close from point n0 to n0 This will permit the condenser 413 tocharge from the power source 414 with current being supplied throughcontact no of switch 410]) and n0 of switch 41112. This latter switch41111 is normally closed to 110 when current is not flowing through therelay coil 411. This condenser 413, which acts as a damping condenser,will charge during the time interval that the motor 101 is running. Assoon as power to the motor 101 is cut off by the reduction of the inputsignal to the amplifier 4113, the condenser 413 will be connected acrossthe terminals of the motor. This occurs when the switch 41Gb closes tocontact 110 The consequent discharge of the damping condenser 413through the motor will cause it to stop immediately. Simultaneously,with the charging of damping condenser 413, the compensation circuitcondenser 416 will also charge. This compensation circuit 416 has itsoutput connection across the lines 404 and 4115 and its output forms aportion of the input into the amplifier 403.

A condenser 416 will charge during the charging of the condenser 413with DC. power being derived from the source 417. This power is appliedacross the condenser 416 when the switch 41Gb is in the 110 position.When the coil 410 is deenergized, the switch 410]) will return to the n0position, permitting the condenser 416 to discharge into the lines 494and 4115. Also illustrated in the.

circuit is a solenoid control circuit 42%. In this circuit the solenoid273 is used to hold the brake previously described in an on position,when the A.C. power supply is on. If the AC. power supply 122 fails, thebrake is off and the fail safe springs cause the valve to open andclose, depending upon which arrangement is used in the manner previouslydescribed.

When the motor 101 is operating in either direction, the switch 410c or4110 will be in its 210 position or nc position, that is, open. Thiswill result in an open circuit through the solenoid 273 and the brakewill be olf. It should be noted that contacts 425 and 424 are normallyopen. When the motor 101 is not operating and the valve is in its properposition, current will be supplied through the solenoid 273 and theswitches nc and n0 which will then be in a closed position. This willactuate the brake and thereby maintain the valve in a locked properposition.

, The contacts 425 and 424 are a second set of contacts in the openlimit and force limit switches provided in the 12 valve to limit themotion of the valve stem. When the valve is closed and the force limitand microswitch become actuated, contact 424, 425 whichever isappropriate, is closed. At this time, this contact, as for example,contact 424, corresponds to the closing direction of the motor and willbe closed. This completes a circuit through the solenoid 273 which willresult in the brake being held on, thus keeping the valve in its closedor open position, as the case may be. When the valve moves from thislimiting position, the switch or contact 424 or 425 will open, thusreleasing the brake and allowing normal operation.

The corresponding switches on the relay 411 act in the same manner by asignal in the amplifier 403 of opposite phase from that in relay coil410.

What is claimed is:

1. In a positioner device of the type described a threaded shaft, meanssupporting said shaft for rotation and longitudinal movement, means forrotating said shaft, a nut threaded thereon adapted to be movedlongitudinally by rotation of said shaft, means for restraining said nutfrom rotation, a sleeve member coaxial with said shaft, bearing meansfixing said sleeve member to said threaded shaft, and spring meansengaging said sleeve member for tensioning said shaft in a longitudinaldirection, said sleeve member adapted to be moved longitudinally onlongitudinal movement of said shaft against the tension of said springmeans for engaging a switch mechanism.

2. In a positioner device of the type described a threaded shaft, meanssupporting said shaft for rotation and longitudinal movement, means forrotating said shaft, a nut threaded thereon adapted to be movedlongitudinally by rotation of said shaft, means for restraining said notfrom rotation, a sleeve member coaxial with said shaft, bearing meansfixing said sleeve member to said threaded shaft, and a loaded springmeans engaging said sleeve member for maintaining said shaft in a fixedlongitudinal position over a selected range of longitudinal forces applied to the shaft, said sleeve member adapted to be movedlongitudinally on longitudinal movement of said shaft against thetension of said spring means for engaging a switch mechanism.

3. A positioner device of the type described in claim 2, having anactuator arm fixed to said nut with a gear mechanism operativelyengaging said arm for controlling an electrical circuit adapted todetermine the position of said arm.

4. A positioner device of the type described in claim 2, wherein saidnut is maintained nonrotatable by an actuator arm secured thereto andmounted for longitudinal movement in a fixed bearing member.

5. A positioner device of the type described for moving an actuatormember between an open and closed position comprising a freely rotatablescrew maintained in a normally fixed longitudinal position, anon-rotatable nut threaded on and adapted to be moved longitudinally byrotation of said shaft and operatively controlling said member, motormeans for rotating said screw, a control mechanism for said motor meansadapted to be engaged respectively by longitudinal movement of saidscrew and movement of said actuator member, said motor means having anarmature shaft in engagement with said screw, electric means for brakingthe rotation of said armature shaft when said motor is inoperative, andmeans for moving said nut to an extreme position when the power to saidelectric means fails.

6. In a positioner device as set forth in claim 5, wherein said motormeans has an armature shaft in engagement with said screw, a brakemechanism mounted on said shaft and operatively engaged by an electricmeans when said motor is disengaged, and spring means engaging said nutadapted to move it to an extreme position when the power to the electricmeans fails and said motor is disengaged.

7. A positioner as set forth in claim 5, having a hand operablemechanism for rotating said shaft and means for disengaging said motormeans from said shaft when said hand operable mechanism is in operation.

8. In a positioner as set forth in claim 2, wherein said means forrotating said shaft comprises a motor, said motor having an armatureshaft, a brake mechanism operatively connected to said armature shaft,electrical means for applying said brake mechanism when said motor isinoperative, and spring means normally maintaining said brake mechanisminoperative.

14 References Cited in the file of this patent UNITED STATES PATENTSOTHER REFERENCES Thaler, G. 1., and Brown, R. G.: Analysis and Design ofFeedback Control Systems, page 579, FIG. C-l; McGraw-Hill, New York,1960.

1. IN A POSITIONER DEVICE OF THE TYPE DESCRIBED A THREADED SHAFT, MEANSSUPPORTING SAID SHAFT FOR ROTATION AND LONGITUDINAL MOVEMENT, MEANS FORROTATING SAID SHAFT, A NUT THREADED THEREON ADAPTED TO BE MOVEDLONGITUDINALLY BY ROTATION OF SAID SHAFT, MEANS FOR RESTRAINING SAID NUTFROM ROTATION, A SLEEVE MEMBER COAXIAL WITH SAID SHAFT, BEARING MEANSFIXING SAID SLEEVE MEMBER TO SAID THREADED SHAFT, AND SPRING MEANSENGAGING SAID SLEEVE MEMBER FOR TENSIONING SAID SHAFT IN A LONGITUDINALDIRECTION, SAID SLEEVE MEMBER ADAPTED TO BE MOVED LONGITUDINALLY ONLONGITUDINAL MOVEMENT OF SAID SHAFT AGAINST THE TENSION OF SAID SPRINGMEANS FOR ENGAGING A SWITCH MECHANISM.